The present invention relates to a one piece structural body with mechanical sensing elements. The sensing elements, designed as flexures, work in connection with strain gauges to provide an accurate hand grip force sensor. Since the grip sensor is light and compact, the grip sensor can be applied to the hand grips of tools and equipment to determine whether the operating forces exerted by the user's hands are within desirable limits.
In the prior art, various grip sensors and pinch sensors have been advanced. For example the sensor shown in U.S. Pat. No. 4,674,330 comprises two parallel handles mounted at one end to a third member. Strain gauges attached to the third member respond in proportion to grip strength when the third member is deflected. However, since the handles are attached only at one end, the third member and thus the strain gauges respond to twisting forces. The net effect is realization of false grip strength measurements. The present invention overcomes this deficiency by using a unitary block of material and incorporating a wheatstone bridge sensor arrangement that cancels out torsion strains developed during testing.
U.S. Pat. No. 1,796,216 teaches a hand held apparatus used for hand muscle development. The apparatus has two spring loaded parts that are gripped and can be clamped together, as well as individual operators for exercising the fingers. The exerciser does not provide for a true readout of forces being generated, nor does it provide parameters for testing a human hand. Therefore, the exerciser is not useful in diagnosing the forces required to operate machines and tools.
Other grip type devices incorporating hydraulic actuation or spring operation have been in use, but these devices are quite large and therefore difficult to use or incorporate for sensing loads on hand held items such as hand tools.